src/runtime/sys_darwin_386.s

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// System calls and other sys.stuff for 386, Darwin
// See http://fxr.watson.org/fxr/source/bsd/kern/syscalls.c?v=xnu-1228
// or /usr/include/sys/syscall.h (on a Mac) for system call numbers.

#include "go_asm.h"
#include "go_tls.h"
#include "textflag.h"

// Exit the entire program (like C exit)
TEXT runtimeexit(SB),NOSPLIT,$0
	MOVL	$1, AX
	INT	$0x80
	MOVL	$0xf1, 0xf1  // crash
	RET

// Exit this OS thread (like pthread_exit, which eventually
// calls __bsdthread_terminate).
TEXT exit1<>(SB),NOSPLIT,$16-0
	// __bsdthread_terminate takes 4 word-size arguments.
	// Set them all to 0. (None are an exit status.)
	MOVL	$0, 0(SP)
	MOVL	$0, 4(SP)
	MOVL	$0, 8(SP)
	MOVL	$0, 12(SP)
	MOVL	$361, AX
	INT	$0x80
	JAE 2(PC)
	MOVL	$0xf1, 0xf1  // crash
	RET

GLOBL exitStack<>(SB),RODATA,$(4*4)
DATA exitStack<>+0x00(SB)/4, $0
DATA exitStack<>+0x04(SB)/4, $0
DATA exitStack<>+0x08(SB)/4, $0
DATA exitStack<>+0x0c(SB)/4, $0

// func exitThread(wait *uint32)
TEXT runtimeexitThread(SB),NOSPLIT,$0-4
	MOVL	wait+0(FP), AX
	// We're done using the stack.
	MOVL	$0, (AX)
	// __bsdthread_terminate takes 4 arguments, which it expects
	// on the stack. They should all be 0, so switch over to a
	// fake stack of 0s. It won't write to the stack.
	MOVL	$exitStack<>(SB), SP
	MOVL	$361, AX	// __bsdthread_terminate
	INT	$0x80
	MOVL	$0xf1, 0xf1  // crash
	JMP	0(PC)

TEXT runtimeopen(SB),NOSPLIT,$0
	MOVL	$5, AX
	INT	$0x80
	JAE	2(PC)
	MOVL	$-1, AX
	MOVL	AX, ret+12(FP)
	RET

TEXT runtimeclosefd(SB),NOSPLIT,$0
	MOVL	$6, AX
	INT	$0x80
	JAE	2(PC)
	MOVL	$-1, AX
	MOVL	AX, ret+4(FP)
	RET

TEXT runtimeread(SB),NOSPLIT,$0
	MOVL	$3, AX
	INT	$0x80
	JAE	2(PC)
	MOVL	$-1, AX
	MOVL	AX, ret+12(FP)
	RET

TEXT runtimewrite(SB),NOSPLIT,$0
	MOVL	$4, AX
	INT	$0x80
	JAE	2(PC)
	MOVL	$-1, AX
	MOVL	AX, ret+12(FP)
	RET

TEXT runtimeraise(SB),NOSPLIT,$0
	// Ideally we'd send the signal to the current thread,
	// not the whole process, but that's too hard on OS X.
	JMP	runtimeraiseproc(SB)

TEXT runtimeraiseproc(SB),NOSPLIT,$16
	MOVL	$20, AX // getpid
	INT	$0x80
	MOVL	AX, 4(SP)	// pid
	MOVL	sig+0(FP), AX
	MOVL	AX, 8(SP)	// signal
	MOVL	$1, 12(SP)	// posix
	MOVL	$37, AX // kill
	INT	$0x80
	RET

TEXT runtimemmap(SB),NOSPLIT,$0
	MOVL	$197, AX
	INT	$0x80
	JAE	ok
	MOVL	$0, p+24(FP)
	MOVL	AX, err+28(FP)
	RET
ok:
	MOVL	AX, p+24(FP)
	MOVL	$0, err+28(FP)
	RET

TEXT runtimemadvise(SB),NOSPLIT,$0
	MOVL	$75, AX
	INT	$0x80
	// ignore failure - maybe pages are locked
	RET

TEXT runtimemunmap(SB),NOSPLIT,$0
	MOVL	$73, AX
	INT	$0x80
	JAE	2(PC)
	MOVL	$0xf1, 0xf1  // crash
	RET

TEXT runtimesetitimer(SB),NOSPLIT,$0
	MOVL	$83, AX
	INT	$0x80
	RET

// OS X comm page time offsets
// http://www.opensource.apple.com/source/xnu/xnu-1699.26.8/osfmk/i386/cpu_capabilities.h
#define	cpu_capabilities	0x20
#define	nt_tsc_base	0x50
#define	nt_scale	0x58
#define	nt_shift	0x5c
#define	nt_ns_base	0x60
#define	nt_generation	0x68
#define	gtod_generation	0x6c
#define	gtod_ns_base	0x70
#define	gtod_sec_base	0x78

// called from assembly
// 64-bit unix nanoseconds returned in DX:AX.
// I'd much rather write this in C but we need
// assembly for the 96-bit multiply and RDTSC.
//
// Note that we could arrange to return monotonic time here
// as well, but we don't bother, for two reasons:
// 1. macOS only supports 64-bit systems, so no one should
// be using the 32-bit code in production.
// This code is only maintained to make it easier for developers
// using Macs to test the 32-bit compiler.
// 2. On some (probably now unsupported) CPUs,
// the code falls back to the system call always,
// so it can't even use the comm page at all.
TEXT runtimenow(SB),NOSPLIT,$40
	MOVL	$0xffff0000, BP /* comm page base */

	// Test for slow CPU. If so, the math is completely
	// different, and unimplemented here, so use the
	// system call.
	MOVL	cpu_capabilities(BP), AX
	TESTL	$0x4000, AX
	JNZ	systime

	// Loop trying to take a consistent snapshot
	// of the time parameters.
timeloop:
	MOVL	gtod_generation(BP), BX
	TESTL	BX, BX
	JZ	systime
	MOVL	nt_generation(BP), CX
	TESTL	CX, CX
	JZ	timeloop
	RDTSC
	MOVL	nt_tsc_base(BP), SI
	MOVL	(nt_tsc_base+4)(BP), DI
	MOVL	SI, 0(SP)
	MOVL	DI, 4(SP)
	MOVL	nt_scale(BP), SI
	MOVL	SI, 8(SP)
	MOVL	nt_ns_base(BP), SI
	MOVL	(nt_ns_base+4)(BP), DI
	MOVL	SI, 12(SP)
	MOVL	DI, 16(SP)
	CMPL	nt_generation(BP), CX
	JNE	timeloop
	MOVL	gtod_ns_base(BP), SI
	MOVL	(gtod_ns_base+4)(BP), DI
	MOVL	SI, 20(SP)
	MOVL	DI, 24(SP)
	MOVL	gtod_sec_base(BP), SI
	MOVL	(gtod_sec_base+4)(BP), DI
	MOVL	SI, 28(SP)
	MOVL	DI, 32(SP)
	CMPL	gtod_generation(BP), BX
	JNE	timeloop

	// Gathered all the data we need. Compute time.
	//	((tsc - nt_tsc_base) * nt_scale) >> 32 + nt_ns_base - gtod_ns_base + gtod_sec_base*1e9
	// The multiply and shift extracts the top 64 bits of the 96-bit product.
	SUBL	0(SP), AX // DX:AX = (tsc - nt_tsc_base)
	SBBL	4(SP), DX

	// We have x = tsc - nt_tsc_base - DX:AX to be
	// multiplied by y = nt_scale = 8(SP), keeping the top 64 bits of the 96-bit product.
	// x*y = (x&0xffffffff)*y + (x&0xffffffff00000000)*y
	// (x*y)>>32 = ((x&0xffffffff)*y)>>32 + (x>>32)*y
	MOVL	DX, CX // SI = (x&0xffffffff)*y >> 32
	MOVL	$0, DX
	MULL	8(SP)
	MOVL	DX, SI

	MOVL	CX, AX // DX:AX = (x>>32)*y
	MOVL	$0, DX
	MULL	8(SP)

	ADDL	SI, AX	// DX:AX += (x&0xffffffff)*y >> 32
	ADCL	$0, DX

	// DX:AX is now ((tsc - nt_tsc_base) * nt_scale) >> 32.
	ADDL	12(SP), AX	// DX:AX += nt_ns_base
	ADCL	16(SP), DX
	SUBL	20(SP), AX	// DX:AX -= gtod_ns_base
	SBBL	24(SP), DX
	MOVL	AX, SI	// DI:SI = DX:AX
	MOVL	DX, DI
	MOVL	28(SP), AX	// DX:AX = gtod_sec_base*1e9
	MOVL	32(SP), DX
	MOVL	$1000000000, CX
	MULL	CX
	ADDL	SI, AX	// DX:AX += DI:SI
	ADCL	DI, DX
	RET

systime:
	// Fall back to system call (usually first call in this thread)
	LEAL	16(SP), AX	// must be non-nil, unused
	MOVL	AX, 4(SP)
	MOVL	$0, 8(SP)	// time zone pointer
	MOVL	$0, 12(SP)	// required as of Sierra; Issue 16570
	MOVL	$116, AX // SYS_GETTIMEOFDAY
	INT	$0x80
	CMPL	AX, $0
	JNE	inreg
	MOVL	16(SP), AX
	MOVL	20(SP), DX
inreg:
	// sec is in AX, usec in DX
	// convert to DX:AX nsec
	MOVL	DX, BX
	MOVL	$1000000000, CX
	MULL	CX
	IMULL	$1000, BX
	ADDL	BX, AX
	ADCL	$0, DX
	RET

// func now() (sec int64, nsec int32, mono uint64)
TEXT timenow(SB),NOSPLIT,$0-20
	CALL	runtimenow(SB)
	MOVL	AX, BX
	MOVL	DX, BP
	SUBL	runtimestartNano(SB), BX
	SBBL	runtimestartNano+4(SB), BP
	MOVL	BX, mono+12(FP)
	MOVL	BP, mono+16(FP)
	MOVL	$1000000000, CX
	DIVL	CX
	MOVL	AX, sec+0(FP)
	MOVL	$0, sec+4(FP)
	MOVL	DX, nsec+8(FP)
	RET

// func nanotime() int64
TEXT runtimenanotime(SB),NOSPLIT,$0
	CALL	runtimenow(SB)
	SUBL	runtimestartNano(SB), AX
	SBBL	runtimestartNano+4(SB), DX
	MOVL	AX, ret_lo+0(FP)
	MOVL	DX, ret_hi+4(FP)
	RET

TEXT runtimesigprocmask(SB),NOSPLIT,$0
	MOVL	$329, AX  // pthread_sigmask (on OS X, sigprocmask==entire process)
	INT	$0x80
	JAE	2(PC)
	MOVL	$0xf1, 0xf1  // crash
	RET

TEXT runtimesigaction(SB),NOSPLIT,$0
	MOVL	$46, AX
	INT	$0x80
	JAE	2(PC)
	MOVL	$0xf1, 0xf1  // crash
	RET

TEXT runtimesigfwd(SB),NOSPLIT,$0-16
	MOVL	fn+0(FP), AX
	MOVL	sig+4(FP), BX
	MOVL	info+8(FP), CX
	MOVL	ctx+12(FP), DX
	MOVL	SP, SI
	SUBL	$32, SP
	ANDL	$~15, SP	// align stack: handler might be a C function
	MOVL	BX, 0(SP)
	MOVL	CX, 4(SP)
	MOVL	DX, 8(SP)
	MOVL	SI, 12(SP)	// save SI: handler might be a Go function
	CALL	AX
	MOVL	12(SP), AX
	MOVL	AX, SP
	RET

// Sigtramp's job is to call the actual signal handler.
// It is called with the following arguments on the stack:
//	0(SP)	"return address" - ignored
//	4(SP)	actual handler
//	8(SP)	siginfo style
//	12(SP)	signal number
//	16(SP)	siginfo
//	20(SP)	context
TEXT runtimesigtramp(SB),NOSPLIT,$20
	MOVL	sig+8(FP), BX
	MOVL	BX, 0(SP)
	MOVL	info+12(FP), BX
	MOVL	BX, 4(SP)
	MOVL	ctx+16(FP), BX
	MOVL	BX, 8(SP)
	CALL	runtimesigtrampgo(SB)

	// call sigreturn
	MOVL	ctx+16(FP), CX
	MOVL	infostyle+4(FP), BX
	MOVL	$0, 0(SP)	// "caller PC" - ignored
	MOVL	CX, 4(SP)
	MOVL	BX, 8(SP)
	MOVL	$184, AX	// sigreturn(ucontext, infostyle)
	INT	$0x80
	MOVL	$0xf1, 0xf1  // crash
	RET

TEXT runtimesigaltstack(SB),NOSPLIT,$0
	MOVL	$53, AX
	INT	$0x80
	JAE	2(PC)
	MOVL	$0xf1, 0xf1  // crash
	RET

TEXT runtimeusleep(SB),NOSPLIT,$32
	MOVL	$0, DX
	MOVL	usec+0(FP), AX
	MOVL	$1000000, CX
	DIVL	CX
	MOVL	AX, 24(SP)  // sec
	MOVL	DX, 28(SP)  // usec

	// select(0, 0, 0, 0, &tv)
	MOVL	$0, 0(SP)  // "return PC" - ignored
	MOVL	$0, 4(SP)
	MOVL	$0, 8(SP)
	MOVL	$0, 12(SP)
	MOVL	$0, 16(SP)
	LEAL	24(SP), AX
	MOVL	AX, 20(SP)
	MOVL	$93, AX
	INT	$0x80
	RET

// func bsdthread_create(stk, arg unsafe.Pointer, fn uintptr) int32
// System call args are: func arg stack pthread flags.
TEXT runtimebsdthread_create(SB),NOSPLIT,$32
	MOVL	$360, AX
	// 0(SP) is where the caller PC would be; kernel skips it
	MOVL	fn+8(FP), BX
	MOVL	BX, 4(SP)	// func
	MOVL	arg+4(FP), BX
	MOVL	BX, 8(SP)	// arg
	MOVL	stk+0(FP), BX
	MOVL	BX, 12(SP)	// stack
	MOVL    $0, 16(SP)      // pthread
	MOVL	$0x1000000, 20(SP)	// flags = PTHREAD_START_CUSTOM
	INT	$0x80
	JAE	4(PC)
	NEGL	AX
	MOVL	AX, ret+12(FP)
	RET
	MOVL	$0, AX
	MOVL	AX, ret+12(FP)
	RET

// The thread that bsdthread_create creates starts executing here,
// because we registered this function using bsdthread_register
// at startup.
//	AX = "pthread" (= 0x0)
//	BX = mach thread port
//	CX = "func" (= fn)
//	DX = "arg" (= m)
//	DI = stack top
//	SI = flags (= 0x1000000)
//	SP = stack - C_32_STK_ALIGN
TEXT runtimebsdthread_start(SB),NOSPLIT,$0
	// set up ldt 7+id to point at m->tls.
	LEAL	m_tls(DX), BP
	MOVL	m_id(DX), DI
	ADDL	$7, DI	// m0 is LDT#7. count up.
	// setldt(tls#, &tls, sizeof tls)
	PUSHAL	// save registers
	PUSHL	$32	// sizeof tls
	PUSHL	BP	// &tls
	PUSHL	DI	// tls #
	CALL	runtimesetldt(SB)
	POPL	AX
	POPL	AX
	POPL	AX
	POPAL

	// Now segment is established. Initialize m, g.
	get_tls(BP)
	MOVL    m_g0(DX), AX
	MOVL	AX, g(BP)
	MOVL	DX, g_m(AX)
	MOVL	BX, m_procid(DX)	// m->procid = thread port (for debuggers)
	CALL	runtimestackcheck(SB)		// smashes AX
	CALL	CX	// fn()
	CALL	exit1<>(SB)
	RET

// func bsdthread_register() int32
// registers callbacks for threadstart (see bsdthread_create above
// and wqthread and pthsize (not used).  returns 0 on success.
TEXT runtimebsdthread_register(SB),NOSPLIT,$40
	MOVL	$366, AX
	// 0(SP) is where kernel expects caller PC; ignored
	MOVL	$runtimebsdthread_start(SB), 4(SP)	// threadstart
	MOVL	$0, 8(SP)	// wqthread, not used by us
	MOVL	$0, 12(SP)	// pthsize, not used by us
	MOVL	$0, 16(SP)	// dummy_value [sic]
	MOVL	$0, 20(SP)	// targetconc_ptr
	MOVL	$0, 24(SP)	// dispatchqueue_offset
	INT	$0x80
	JAE	4(PC)
	NEGL	AX
	MOVL	AX, ret+0(FP)
	RET
	MOVL	$0, AX
	MOVL	AX, ret+0(FP)
	RET

// Invoke Mach system call.
// Assumes system call number in AX,
// caller PC on stack, caller's caller PC next,
// and then the system call arguments.
//
// Can be used for BSD too, but we don't,
// because if you use this interface the BSD
// system call numbers need an extra field
// in the high 16 bits that seems to be the
// argument count in bytes but is not always.
// INT $0x80 works fine for those.
TEXT runtimesysenter(SB),NOSPLIT,$0
	POPL	DX
	MOVL	SP, CX
	BYTE $0x0F; BYTE $0x34;  // SYSENTER
	// returns to DX with SP set to CX

TEXT runtimemach_msg_trap(SB),NOSPLIT,$0
	MOVL	$-31, AX
	CALL	runtimesysenter(SB)
	MOVL	AX, ret+28(FP)
	RET

TEXT runtimemach_reply_port(SB),NOSPLIT,$0
	MOVL	$-26, AX
	CALL	runtimesysenter(SB)
	MOVL	AX, ret+0(FP)
	RET

TEXT runtimemach_task_self(SB),NOSPLIT,$0
	MOVL	$-28, AX
	CALL	runtimesysenter(SB)
	MOVL	AX, ret+0(FP)
	RET

// Mach provides trap versions of the semaphore ops,
// instead of requiring the use of RPC.

// func mach_semaphore_wait(sema uint32) int32
TEXT runtimemach_semaphore_wait(SB),NOSPLIT,$0
	MOVL	$-36, AX
	CALL	runtimesysenter(SB)
	MOVL	AX, ret+4(FP)
	RET

// func mach_semaphore_timedwait(sema, sec, nsec uint32) int32
TEXT runtimemach_semaphore_timedwait(SB),NOSPLIT,$0
	MOVL	$-38, AX
	CALL	runtimesysenter(SB)
	MOVL	AX, ret+12(FP)
	RET

// func mach_semaphore_signal(sema uint32) int32
TEXT runtimemach_semaphore_signal(SB),NOSPLIT,$0
	MOVL	$-33, AX
	CALL	runtimesysenter(SB)
	MOVL	AX, ret+4(FP)
	RET

// func mach_semaphore_signal_all(sema uint32) int32
TEXT runtimemach_semaphore_signal_all(SB),NOSPLIT,$0
	MOVL	$-34, AX
	CALL	runtimesysenter(SB)
	MOVL	AX, ret+4(FP)
	RET

// func setldt(entry int, address int, limit int)
// entry and limit are ignored.
TEXT runtimesetldt(SB),NOSPLIT,$32
	MOVL	address+4(FP), BX	// aka base

	/*
	 * When linking against the system libraries,
	 * we use its pthread_create and let it set up %gs
	 * for us.  When we do that, the private storage
	 * we get is not at 0(GS) but at 0x468(GS).
	 * 8l rewrites 0(TLS) into 0x468(GS) for us.
	 * To accommodate that rewrite, we translate the
	 * address and limit here so that 0x468(GS) maps to 0(address).
	 *
	 * See cgo/gcc_darwin_386.c:/468 for the derivation
	 * of the constant.
	 */
	SUBL	$0x468, BX

	/*
	 * Must set up as USER_CTHREAD segment because
	 * Darwin forces that value into %gs for signal handlers,
	 * and if we don't set one up, we'll get a recursive
	 * fault trying to get into the signal handler.
	 * Since we have to set one up anyway, it might as
	 * well be the value we want.  So don't bother with
	 * i386_set_ldt.
	 */
	MOVL	BX, 4(SP)
	MOVL	$3, AX	// thread_fast_set_cthread_self - machdep call #3
	INT	$0x82	// sic: 0x82, not 0x80, for machdep call

	XORL	AX, AX
	MOVW	GS, AX
	RET

TEXT runtimesysctl(SB),NOSPLIT,$0
	MOVL	$202, AX
	INT	$0x80
	JAE	4(PC)
	NEGL	AX
	MOVL	AX, ret+24(FP)
	RET
	MOVL	$0, AX
	MOVL	AX, ret+24(FP)
	RET

// func kqueue() int32
TEXT runtimekqueue(SB),NOSPLIT,$0
	MOVL	$362, AX
	INT	$0x80
	JAE	2(PC)
	NEGL	AX
	MOVL	AX, ret+0(FP)
	RET

// func kevent(kq int32, ch *keventt, nch int32, ev *keventt, nev int32, ts *timespec) int32
TEXT runtimekevent(SB),NOSPLIT,$0
	MOVL	$363, AX
	INT	$0x80
	JAE	2(PC)
	NEGL	AX
	MOVL	AX, ret+24(FP)
	RET

// func closeonexec(fd int32)
TEXT runtimecloseonexec(SB),NOSPLIT,$32
	MOVL	$92, AX  // fcntl
	// 0(SP) is where the caller PC would be; kernel skips it
	MOVL	fd+0(FP), BX
	MOVL	BX, 4(SP)  // fd
	MOVL	$2, 8(SP)  // F_SETFD
	MOVL	$1, 12(SP)  // FD_CLOEXEC
	INT	$0x80
	JAE	2(PC)
	NEGL	AX
	RET